In view of current economic conditions, substantial attention has been given to the recycle of used structural components in new construction and in general maintenance. The use of used structural components can be an economic benefit since the cost of new materials is often substantially greater than the cost of obtaining the used material. Such recycle can be effective if the recycled material is structurally sound. Structurally sound recycled structural components can often be obtained if the components are repaired.
In the instance that the structural components are formed from materials such as wood, plastic, concrete and others, surface defects must be repaired before the component can be reused. Such defects can appear as cuts, gaps, deep holes, cracks, etc. Such defects can substantially reduce the value of the recycled component in new construction since the defect can result in a fastener having an imperfect bond to a structural member, the defect can be aesthetically unpleasing or the defect can reduce the structural strength of the member.
Materials used to repair surface defects in structural members should have certain characteristics. The material should be easily applied and should form high strength bonds to structural members made of varying materials. The repair materials should be usable in many environments including environments having extremes of heat and cold and having the presence of substantial quantities of environmental water.
One particularly important end use for such repair compositions is in the recycle or reuse of railroad ties. Typically in the maintenance of the railroad right of way the railroad rails, along with the tie plates and spikes, are removed from railroad ties which remain in the roadbed. If a new rail is to be spiked to the old tie, it is critical that the railroad tie spike holes be repaired prior to laying the new rail. The presence of spike holes in an old tie can cause problems since if a spike is driven into a portion of the tie near an old spike hole, the driving force of the spike can displace the spike from its intended location into an old hole, displacing the rail, tie plate and spike. In the instance that the spike is driven into incorrect location substantial economic loss can result in repairing the misaligned rail. If a misaligned rail is not repaired, the defect can cause derailment or other problems. Further, the spike holes can be the source of structural weakness in the tie.
Mechanical spike hole repair means have been suggested in the art in for example, Moses, U.S. Pat. No. 3,191,864 which teaches a mechanical spike hole insert used by first boring out an old spike hole, installing an insert and driving a new spike into the insert; and Newman, U.S. Pat. No. 3,716,608, which teaches metallic inserts that can be placed in bored out spike holes with a filling of a synthetic resin into which the spikes can be driven. In another area of repair, Tessenski, U.S. Pat. Nos. 4,070,201 and 4,152,185, teach a railroad tie spike hole plugging material and method using a substantial uniform mixture of a granular abrasive material and a granular plastic material which is poured into the hole left after spike removal. The driving force of a spike into the abrasive material generates heat which plasticizes the material resulting in a firm bond of the spike to the material. Mechanical and resin-based hole filling methods tend to be time consuming, expensive and adapted to manual not automatic application or installation.
Rhodes et al, U.S. Pat. No. 4,295,259, teaches a method of reusing wooden railroad ties in which spike holes are filled with a high-density, polyurethane foam composition. We have found that the use of polyurethane foam in filling spike holes in used railroad ties can present significant problems. The polyurethane foam compositions do not appear to adhere to a spike hole with sufficient adhesion to prevent the accidental removal of the foam repair mass during the repair and subsequent mechanical rail installation. Further, the urethane foams of the prior art tend to foam uncontrollably in the presence of substantial environmental moisture. Since, the moisture tends to accelerate the foaming properties of the urethane composition, the presence of water can cause the too rapid formation of a foam mass of low strength and density and can result in the formation of an incomplete or unreliable repair.
Accordingly, a substantial need exists in the art for compositions that can be used to repair surface defects on structural components such a railroad ties which provide a repair mass having strong adhesion to the substrate structural member, can be used in the presence of substantial quantities of environmental water and can be used in automatic application equipment.